Double diaphragm pump



FIG. 1 is a front elevational view of a double diaphragm pump showing my new design;

FIG. 2 is an elevational view of one side thereof, the other side being a mirror image;

FIG. 3 is a back elevational view thereof; and

FIG. 4 is a top plan view thereof. 

The ornamental design for a double diaphragm pump, substantially as shown and described. 